We propose to use selected mutants and recombinant DNA's to study two objectives related to tRNA function: 1) Plasmids containing tRNA genes will be manipulated in vitro to produce new species of tRNA in vivo in order to study the effects of tRNA sequence on function. Some tRNA mutants will be used for the same purposes. 2) Plasmids containing a regulatory locus in the stringent-relaxed control circuit will be used to study the control of stable RNA synthesis.